Performance and mechanism of sodium citrate pretreatment to promote waste activated sludge disintegration and short-chain fatty acid production during anaerobic fermentation

Waste activated sludge (WAS) contains massive organic matter that can be used for resource recovery. Anaerobic fermentation to produce short-chain fatty acids (SCFAs) is recognized as an expedient and efficient measure to recycle sludge resource. Complexing agents have been reported to be effective in disintegrating extracellular polymeric substances (EPS) and increasing the rate of sludge hydrolysis. This study investigated the performance and mechanism of sodium citrate (SC) pretreatment to promote the disintegration of WAS and the production of SCFAs by anaerobic fermentation. The results showed that when SC dosage was 0.25 g/g TSS, both EPS and cell membrane were destroyed. Among them, the soluble protein and polysaccharide in the supernatant reached 1 072 & PLUSMN; 15 mg COD/L and 233 mg COD/L, and DNA reached 175 & PLUSMN; 3 mg/L at the fifth hour. Damage of EPS is mainly reflected in S-EPS and LB-EPS, while it is not obvious in TB-EPS. The SC pretreated group was much higher in SCFAs production, and the SC dosing of 0.25 g/g TSS group reached the peak acid production of 7 677 & PLUSMN; 350 mg COD/L on the third day, which was 8.3 times higher than that of the control group. Moreover, SC was able to increase the hydrolytic enzyme activity and inhibit the coenzyme F420 activity, which increased the production of SCFAs and decreased its consumption rate.

Automated summary

This study investigated the performance and mechanism of sodium citrate pretreatment to promote the disintegration of waste activated sludge (WAS) and the production of short-chain fatty acids (SCFAs) by anaerobic fermentation. The results showed that SC pretreatment increased SCFAs production by 8.3 times compared to the control group. Moreover, SC increased hydrolytic enzyme activity and inhibited coenzyme F420 activity, leading to increased SCFAs production and decreased consumption rate.